Specs and limits

Slack specs and limits

Slack text is limited to 4,000 characters, counted by code points. This page lists every text, media and posting rule 1Post checks for Slack: counts, sizes, lengths, threads and the daily cap. Where Slack publishes a figure on its own page we cite it with the date we read it.

Also:Schedule Slack posts Social media posting limits by network Social media posting limits table

Updated 2026-10-26

What 1Post checks for Slack

Rule	What 1Post checks
Text limit	4,000 characters, counted by code points
Media accepted	Text only
Threads	No
First comment	No
Posts per day, per connected account (1Post)	100

These are the limits 1Post applies in the composer, so a post that passes is not refused for them when it is sent. A network can still refuse a post for reasons outside these rules, such as its content policies.

What Slack publishes

Fact	Source
Slack suggests keeping message text to 4,000 characters for best results and truncates messages over 40,000.	Slack developer docs: chat.postMessage, read 2026-10-26

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Questions

How is Slack text counted?

Slack text is counted by code points. The character counter applies the same rule.

Where do these Slack limits come from?

They are the limits 1Post checks before a post is sent. Figures the network publishes on its own page are cited above with the date read; the rest are checks 1Post sets.

How often is this page updated?

When a network changes a rule or we read a newer figure, the page changes with it. The date at the top shows the last change.